We propose to use MRM to investigate the integration of skeletal and neural components during craniofacial development in Monodelphis domestica (opossum). Monodelphis is an interesting animal model for craniofacial development because development of oral skeletal structures are accelerated (compared to placental mammals) while the nervous system is delayed in development. We will focus on two ages -- the day of birth (equivalent to a mouse at embryonic day 12), and approximately 20 days after birth. We will determine whether there is sufficient contrast and resolution (at 9 Tesla) to follow the differentiation of the neural tissues and skeletal elements of the head. We hope to compare various fixation strengths and times, in order to find the optimal preparation of these specimens. Most techniques that allow the assessment of growth of tissues either cause excessive shrinkage, particularly of neural tissue (e.g., histology), or destroy the skeletal elements (removing the brain and weighing it). MR microscopy will allow the assessment of brain growth, while preserving the specimen for various techniques to study skeletal differentiation. (Please see attachment for a more detailed description of this work and examples of recent publications on this work).